Patent GB-607379-A (GB)
Title: Improvements in or relating to electrical signalling systems
IPC: B66B19/06
Filed: 1946-02-01
Abstract: 607,379. Electric selective signalling. AUTOMATIC TELEPHONE & ELECTRIC CO., Ltd., STONOR, C. R. P., and HOLLAND, T. Feb. 1, 1946, No. 3215. [Class 40 (i)] A system for transmitting signals from any one of a plurality of signalling points LSA, LSB ... &c. along a common signalling circuit 10, 11, 12, to indicate the location of the signalling point at a control'point, includes, in the signalling circuit, a chain of magnetic locking relays MLA, MLB ... one for each signalling point, and a signalling operation causes the simultaneous operation of a number of these relays characteristic of the signalling point, the operated relays being then automatically restored to normal in succession and the number of relays so restored being counted, e.g. by an impulse-operated relay-chain adapted to give a visual indication of the number of impulses and hence of the signalling point. Stop-signalling. As applied to a minehaulage system the two wires 10, 11 are bare and a stop signal is initiated from a signalling point by shorting the wires 10, 11 thereat. If such a signal is initiated in section LSC, for example, a circuit is made from positive over resistance YC contacts DY2, B3, windings of relays ST, MLA, MLB, MLC, line 10, contacts DY1 to negative. These four relays energize and relay ST locks over its lower winding and contacts ST1. At contacts ST2 lines 13, 14 are connected to ring the signalling bell at the engineman's position and at ST3 a slow-tooperate relay B is energized. The line relays MLA ... are of the magnetic locking type, being operated by energization of either of their two windings in the directions of the arrows shown and restored to normal only by a reverse current in either winding. Relays MLA-MLC operate to prepare restoring circuits for their lower windings. After a slight interval relay B operates and locks over contacts B1. At contacts B2 the locking circuit of relay ST is opened and at B3 the short-circuit is removed from a high resistance relay CR. After a further short interval, relay ST releases to open the bell circuit at ST2. Over contacts B4, LOI, MLAI, DYI a relay P is energized in series with the lower winding of relay MLA. Relay MLA is thereby restored and relay P which locks over contacts P4 transmits an impulse to a counting relay chain over contacts P2. At contacts P1 a slow-to-operate relay LO is energized, at P3 a relay YT is energized. Relay LO operates after its delay period and at contacts LOI short-circuits relay P which releases after a short interval and opens the circuit of relay LO which releases in turn and again completes a circuit for relay P. The release of P removes the short-circuit from a relay DY which operates, locks over its lower winding at contacts DY3, and at contacts DY1, DY2 reverses the current to lines 10, 11. Relay MLA having restored, relay P is reenergized in series with the lower winding of relay MLB and the line current being reversed causes MLB to restore at the same time as an impulse is sent to the counter over P2. As MLB restores the line circuit is transferred to relay MLC. Relays P, LO operate as before, relay DY, however, restoring as P releases, thereby restoring the normal supply connections to the signalling leads. The operation is now repeated to restore relay MLC and relays YT, DT are again operated. Since, however, relay MLD is not operated no further circuit is completed for relay P and all relays except B and DY, YT (if operated) revert to normal. The relay counting chain is arranged to complete lamp circuits which indicate the operative signalling point to the engineman. He will accordingly stop the engine and momentarily operate the cancel key KC to.restore relay B, other contacts of key KC causing the indicator lamp to flash instead of being lighted steadily. The release of relay B short-circuits the relay CR and releases relays DY, YT (if operated), the system then being ready to receive further signals. Start signalling. The start signal comprises two impulses, the first of which produces similar effects to those above described. If this first impulse comes from the same section as the previous stop signal or similar number of pulses is transmitted to the indicator which is so arranged that steady lighting of the appropriate lamp is thereby produced. The second impulse will arrive when relay B is still operated so that high resistance relay CR is in the signalling circuit. Its resistance is such as to prevent relays ST and the various ML relays from operating, but relay CR itself pulls up to operate the signalling bell over contacts CR1. Relay CR is connected to line through a rectifier bridge so that it may operate irrespective of the direction of the line current. The engineman may now restart the engine and operate the same or a further cancel key to extinguish the lamp and restore the whole system to normal, i.e. with engine running and nothing showing on the indicator. If the start signal has come from some other section, the lamp appropriate thereto will be lighted steadily while the original lamp continues to flash. The engine then wipes out the spurious signal by operating the cancel key which will not affect the flashing lamp.